#include "cuda_runtime.h"
#include "cuda_runtime_internal.h"
#include "host_api.hpp"
#include <cstdio>
#include <cstring>
#include <cstdlib>

// Global error state
static cudaError_t g_lastError = cudaSuccess;

// Error strings
static const char* errorStrings[] = {
    "cudaSuccess",
    "cudaErrorInvalidValue",
    "cudaErrorMemoryAllocation",
    "cudaErrorInitializationError",
    // ... add more as needed
    "cudaErrorUnknown"
};

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @brief Memory management functions
 */

cudaError_t cudaMalloc(void** devPtr, size_t size) {
    auto& state = ptxrt::internal::RuntimeState::getInstance();
    CUdeviceptr ptr;
    
    CUresult result = state.host_api.cuMemAlloc(&ptr, size);
    if (result != CUDA_SUCCESS) {
        state.last_error = cudaErrorMemoryAllocation;
        return cudaErrorMemoryAllocation;
    }
    
    *devPtr = reinterpret_cast<void*>(ptr);
    
    // Track allocation
    ptxrt::internal::DeviceMemory mem;
    mem.host_ptr = *devPtr;
    mem.size = size;
    mem.is_freed = false;
    state.device_memory[*devPtr] = mem;
    
    return cudaSuccess;
}

cudaError_t cudaFree(void* devPtr) {
    if (!devPtr) {
        return cudaSuccess;
    }
    
    auto& state = ptxrt::internal::RuntimeState::getInstance();
    CUdeviceptr ptr = reinterpret_cast<CUdeviceptr>(devPtr);
    
    CUresult result = state.host_api.cuMemFree(ptr);
    
    // Remove from tracking
    state.device_memory.erase(devPtr);
    
    if (result != CUDA_SUCCESS) {
        state.last_error = cudaErrorUnknown;
        return cudaErrorUnknown;
    }
    
    return cudaSuccess;
}

cudaError_t cudaMemcpy(void* dst, const void* src, size_t count, enum cudaMemcpyKind kind) {
    auto& state = ptxrt::internal::RuntimeState::getInstance();
    CUresult result;
    
    switch (kind) {
        case cudaMemcpyHostToDevice:
            result = state.host_api.cuMemcpyHtoD(
                reinterpret_cast<CUdeviceptr>(dst), src, count);
            break;
            
        case cudaMemcpyDeviceToHost:
            result = state.host_api.cuMemcpyDtoH(
                dst, reinterpret_cast<CUdeviceptr>(src), count);
            break;
            
        case cudaMemcpyDeviceToDevice:
            // Not yet supported
            state.last_error = cudaErrorInvalidMemcpyDirection;
            return cudaErrorInvalidMemcpyDirection;
            
        case cudaMemcpyHostToHost:
            memcpy(dst, src, count);
            return cudaSuccess;
            
        default:
            state.last_error = cudaErrorInvalidMemcpyDirection;
            return cudaErrorInvalidMemcpyDirection;
    }
    
    if (result != CUDA_SUCCESS) {
        state.last_error = cudaErrorUnknown;
        return cudaErrorUnknown;
    }
    
    return cudaSuccess;
}

cudaError_t cudaMemset(void* devPtr, int value, size_t count) {
    // TODO: Implement device memory set
    (void)devPtr;
    (void)value;
    (void)count;
    return cudaSuccess;
}

/**
 * @brief Device management functions
 */

cudaError_t cudaDeviceSynchronize(void) {
    // TODO: Implement device synchronization
    return cudaSuccess;
}

cudaError_t cudaDeviceReset(void) {
    // TODO: Implement device reset
    return cudaSuccess;
}

cudaError_t cudaGetDeviceCount(int* count) {
    // TODO: Implement get device count
    if (count) {
        *count = 1; // Simulate 1 device
    }
    return cudaSuccess;
}

cudaError_t cudaSetDevice(int device) {
    // TODO: Implement set device
    (void)device;
    return cudaSuccess;
}

cudaError_t cudaGetDevice(int* device) {
    // TODO: Implement get device
    if (device) {
        *device = 0; // Simulate device 0
    }
    return cudaSuccess;
}

/**
 * @brief Error handling functions
 */

const char* cudaGetErrorString(cudaError_t error) {
    // TODO: Implement proper error string lookup
    if (error == cudaSuccess) {
        return errorStrings[0];
    }
    return "Unknown error";
}

cudaError_t cudaGetLastError(void) {
    cudaError_t error = g_lastError;
    g_lastError = cudaSuccess;
    return error;
}

cudaError_t cudaPeekAtLastError(void) {
    return g_lastError;
}

/**
 * @brief Kernel launch functions
 */

// Thread-local storage for <<<>>> syntax
static thread_local ptxrt::internal::LaunchConfig* g_current_config = nullptr;

cudaError_t cudaLaunchKernel(const void* func, dim3 gridDim, dim3 blockDim,
                             void** args, size_t sharedMem, cudaStream_t stream) {
    auto& state = ptxrt::internal::RuntimeState::getInstance();
    
    // 1. Find kernel info (if registered via nvcc)
    std::string kernel_name;
    auto it = state.kernel_map.find(func);
    if (it != state.kernel_map.end()) {
        kernel_name = it->second.kernel_name;
        printf("[libptxrt] Launching registered kernel: %s\n", kernel_name.c_str());
    } else {
        // For clang-compiled code, kernel is not registered
        // We'll load PTX and use the first kernel found
        printf("[libptxrt] Kernel not registered (clang mode), will use PTX entry point\n");
        kernel_name = "";  // Will be determined from PTX
    }
    
    printf("[libptxrt] Grid: (%u,%u,%u) Block: (%u,%u,%u)\n",
           gridDim.x, gridDim.y, gridDim.z,
           blockDim.x, blockDim.y, blockDim.z);
    
    // 2. Load PTX program (first time only)
    if (!state.program_loaded) {
        // Get PTX path from environment variable
        const char* ptx_path = getenv("PTXRT_PTX_PATH");
        if (!ptx_path) {
            fprintf(stderr, "[libptxrt] ERROR: PTXRT_PTX_PATH environment variable not set\n");
            fprintf(stderr, "[libptxrt] Please set it to point to your .ptx file\n");
            state.last_error = cudaErrorInvalidSource;
            return cudaErrorInvalidSource;
        }
        
        state.ptx_file_path = ptx_path;
        printf("[libptxrt] Loading PTX: %s\n", state.ptx_file_path.c_str());
        
        if (!state.host_api.loadProgram(state.ptx_file_path)) {
            fprintf(stderr, "[libptxrt] ERROR: Failed to load PTX from %s\n", 
                    state.ptx_file_path.c_str());
            state.last_error = cudaErrorInvalidSource;
            return cudaErrorInvalidSource;
        }
        
        state.program_loaded = true;
        printf("[libptxrt] PTX loaded successfully\n");
    }
    
    // 3. Launch kernel via HostAPI
    // Note: CUfunction is uint32_t, we use 0 for now
    // The actual kernel will be found by name in the loaded PTX
    CUfunction f = 0;
    
    CUresult result = state.host_api.cuLaunchKernel(
        f,
        gridDim.x, gridDim.y, gridDim.z,
        blockDim.x, blockDim.y, blockDim.z,
        sharedMem,
        nullptr,  // stream
        args,
        nullptr   // extra
    );
    
    if (result != CUDA_SUCCESS) {
        fprintf(stderr, "[libptxrt] ERROR: Kernel launch failed with code %d\n", result);
        state.last_error = cudaErrorLaunchFailure;
        return cudaErrorLaunchFailure;
    }
    
    printf("[libptxrt] Kernel launched successfully\n");
    
    (void)stream;
    return cudaSuccess;
}

cudaError_t cudaConfigureCall(dim3 gridDim, dim3 blockDim, size_t sharedMem, cudaStream_t stream) {
    // Create or reset configuration
    if (!g_current_config) {
        g_current_config = new ptxrt::internal::LaunchConfig();
    } else {
        g_current_config->args.clear();
        g_current_config->arg_sizes.clear();
    }
    
    g_current_config->grid_dim = gridDim;
    g_current_config->block_dim = blockDim;
    g_current_config->shared_mem = sharedMem;
    g_current_config->stream = stream;
    
    return cudaSuccess;
}

cudaError_t cudaSetupArgument(const void* arg, size_t size, size_t offset) {
    if (!g_current_config) {
        fprintf(stderr, "[libptxrt] ERROR: cudaSetupArgument called without cudaConfigureCall\n");
        return cudaErrorInvalidValue;
    }
    
    // Copy argument data
    void* arg_copy = malloc(size);
    if (!arg_copy) {
        return cudaErrorMemoryAllocation;
    }
    memcpy(arg_copy, arg, size);
    
    g_current_config->args.push_back(arg_copy);
    g_current_config->arg_sizes.push_back(size);
    
    (void)offset;  // Offset is implicit from order
    return cudaSuccess;
}

cudaError_t cudaLaunch(const void* func) {
    if (!g_current_config) {
        fprintf(stderr, "[libptxrt] ERROR: cudaLaunch called without configuration\n");
        return cudaErrorInvalidValue;
    }
    
    // Prepare argument array
    void** args = g_current_config->args.empty() ? nullptr : g_current_config->args.data();
    
    // Call cudaLaunchKernel
    cudaError_t result = cudaLaunchKernel(
        func,
        g_current_config->grid_dim,
        g_current_config->block_dim,
        args,
        g_current_config->shared_mem,
        g_current_config->stream
    );
    
    // Clean up argument copies
    for (void* arg : g_current_config->args) {
        free(arg);
    }
    g_current_config->args.clear();
    g_current_config->arg_sizes.clear();
    
    return result;
}

/**
 * @brief Registration functions (called by CUDA compiler-generated code)
 */

void** __cudaRegisterFatBinary(void* fatCubin) {
    // Simplified version: don't parse fat binary
    // User should provide PTX file via PTXRT_PTX_PATH environment variable
    
    static void* handle = malloc(8);
    
    printf("[libptxrt] Fat binary registered at %p\n", fatCubin);
    printf("[libptxrt] NOTE: Please set PTX file via PTXRT_PTX_PATH environment variable\n");
    
    return &handle;
}

void __cudaUnregisterFatBinary(void** fatCubinHandle) {
    // TODO: Implement fat binary unregistration and cleanup
    printf("[libptxrt] Fat binary unregistered\n");
    (void)fatCubinHandle;
}

void __cudaRegisterFunction(void** fatCubinHandle,
                           const char* hostFun,
                           char* deviceFun,
                           const char* deviceName,
                           int thread_limit,
                           uint3* tid,
                           uint3* bid,
                           dim3* bDim,
                           dim3* gDim,
                           int* wSize) {
    auto& state = ptxrt::internal::RuntimeState::getInstance();
    
    ptxrt::internal::KernelInfo info;
    info.kernel_name = deviceName;
    info.host_func = (const void*)hostFun;
    info.thread_limit = thread_limit;
    info.ptx_code = nullptr;  // Will be set when PTX is loaded
    
    state.kernel_map[(const void*)hostFun] = info;
    
    printf("[libptxrt] Kernel registered: %s at %p\n", deviceName, hostFun);
    
    (void)fatCubinHandle;
    (void)deviceFun;
    (void)tid;
    (void)bid;
    (void)bDim;
    (void)gDim;
    (void)wSize;
}

void __cudaRegisterVar(void** fatCubinHandle,
                      char* hostVar,
                      char* deviceAddress,
                      const char* deviceName,
                      int ext,
                      size_t size,
                      int constant,
                      int global) {
    // TODO: Implement variable registration
    (void)fatCubinHandle;
    (void)hostVar;
    (void)deviceAddress;
    (void)deviceName;
    (void)ext;
    (void)size;
    (void)constant;
    (void)global;
}

void __cudaRegisterManagedVar(void** fatCubinHandle,
                              void** hostVarPtrAddress,
                              char* deviceAddress,
                              const char* deviceName,
                              int ext,
                              size_t size,
                              int constant,
                              int global) {
    // TODO: Implement managed variable registration
    (void)fatCubinHandle;
    (void)hostVarPtrAddress;
    (void)deviceAddress;
    (void)deviceName;
    (void)ext;
    (void)size;
    (void)constant;
    (void)global;
}

/**
 * @brief Stream management functions
 */

cudaError_t cudaStreamCreate(cudaStream_t* pStream) {
    // TODO: Implement stream creation
    (void)pStream;
    return cudaSuccess;
}

cudaError_t cudaStreamDestroy(cudaStream_t stream) {
    // TODO: Implement stream destruction
    (void)stream;
    return cudaSuccess;
}

cudaError_t cudaStreamSynchronize(cudaStream_t stream) {
    // TODO: Implement stream synchronization
    (void)stream;
    return cudaSuccess;
}

/**
 * @brief Event management functions
 */

cudaError_t cudaEventCreate(cudaEvent_t* event) {
    // TODO: Implement event creation
    (void)event;
    return cudaSuccess;
}

cudaError_t cudaEventDestroy(cudaEvent_t event) {
    // TODO: Implement event destruction
    (void)event;
    return cudaSuccess;
}

cudaError_t cudaEventRecord(cudaEvent_t event, cudaStream_t stream) {
    // TODO: Implement event recording
    (void)event;
    (void)stream;
    return cudaSuccess;
}

cudaError_t cudaEventSynchronize(cudaEvent_t event) {
    // TODO: Implement event synchronization
    (void)event;
    return cudaSuccess;
}

cudaError_t cudaEventElapsedTime(float* ms, cudaEvent_t start, cudaEvent_t end) {
    // TODO: Implement elapsed time calculation
    (void)ms;
    (void)start;
    (void)end;
    if (ms) {
        *ms = 0.0f;
    }
    return cudaSuccess;
}

/**
 * @brief CUDA kernel configuration push/pop functions (used by <<<>>> syntax)
 */

// These functions are called by compiler-generated code for <<<>>> syntax
unsigned __cudaPushCallConfiguration(dim3 gridDim, dim3 blockDim, size_t sharedMem, void* stream) {
    cudaError_t err = cudaConfigureCall(gridDim, blockDim, sharedMem, (cudaStream_t)stream);
    return (err == cudaSuccess) ? 0 : 1;
}

cudaError_t __cudaPopCallConfiguration(dim3 *gridDim, dim3 *blockDim, size_t *sharedMem, void **stream) {
    if (!g_current_config) {
        return cudaErrorInvalidValue;
    }
    
    if (gridDim) *gridDim = g_current_config->grid_dim;
    if (blockDim) *blockDim = g_current_config->block_dim;
    if (sharedMem) *sharedMem = g_current_config->shared_mem;
    if (stream) *stream = g_current_config->stream;
    
    return cudaSuccess;
}

#ifdef __cplusplus
}
#endif
